Police have appealed for help in the investigation into the "execution style" killing of Sydney father-of-four John Gasovski, whose body was found dumped in bushland off Jamberoo Mountain Road in June.

Mr Gasovski was shot once in the back of the head, and police believe he may have been killed by organised crime figures whom he had become involved with.

A park ranger found his body early on June 15, but police have yet to recover the murder weapon.

Now, detectives investigating the murder are appealing to members of the public who may have seen him in the hours before his death.

Hyndai iLoad van similar to John Gasovski's placed at the scene to help jog drivers' memories. Picture: NSW POLICE

On Tuesday, they conducted a large police operation at Pheasants Nest, searching the bushland where his van was found.

Mr Gasovski's wife, Jackie, will read a statement at a media conference on Wednesday morning.

About 4.40pm on June 9, the 48-year-old father left his home in Arncliffe, telling his family he was heading to Canberra for work and would be back home the following night.

By June 12, Mr Gasovski had still not returned home, prompting his worried family to contact police.

Three days later, around 8.45am on June 15, police from Lake Illawarra Local Area Command were called to Jamberoo Mountain Road, Budderoo, after a park ranger found the body of a man.

A post mortem examination confirmed Mr Gasovski had sustained a gunshot wound to the head.

Strike Force Berek, comprising detectives from the Homicide Squad and police from St George and Lake Illawarra Local Area Commands, was formed to investigate Mr Gasovski’s death.

As part of their inquiries to date, detectives have been tracking Mr Gasovski’s movements on the day he left Sydney – Monday June 9.

Of note:

- Detectives have been told Mr Gasovski departed his Arncliffe home in his grey Hyundai iLoad van (NSW registration – BJQ82K) at shortly before 5.00pm, telling his family he was heading to Canberra on business and would be back in Sydney the following evening

- An hour later, his van passed through the M5 tollway at Moorebank

- About 7.30pm, Mr Gasovski was sighted at a service centre on the corner of the Hume Highway and Sallys Corner Road, Suttons Forest

- Circumstances suggest that after leaving the service centre in Suttons Forest, Mr Gasovski may have turned around and driven his van north to a service centre on the northbound side of the Hume Motorway in Pheasants Nest, arriving shortly after 9pm

- After returning to the northbound side of the Pheasants Nest service centre, detectives believe his vehicle was also sighted soon after on the southbound side.

Mr Gasovski’s van was found on Monday June 23, abandoned on the slipway leading out of the southbound service centre in Pheasants Nest. It is not known how long it was there for.

The Commander of the Homicide Squad, Detective Superintendent Mick Willing, said police were keen for any motorists who passed through Pheasants Nest, Suttons Forest, Jamberoo or other parts of southern NSW between Monday June 9 and Monday June 23, to jog their memories for any suspicious behaviour they may have seen inside a service station or on the open road.

“A lot of motorists now have mounted in-car cameras on their dashboards, recording as they drive," he said.

“If you are one of these motorists and you passed through the Pheasants Nest area between June 9 and June 23, please contact Crime Stoppers or send your video to us directly by uploading it via the ‘Help us solve a crime’ link on the NSW Police website.

“Any information you have, no matter how small or insignificant it may seem, could prove crucial in helping us solve this case.”

Detective Superintendent Willing said police had conducted a number of searches in recent days in a bid to find any more information or evidence that could help them piece together Mr Gasovski’s final movements.

“Last Thursday, officers conducted a search of bushland in Jamberoo, near where Mr Gasovski’s body was found,” he said.

“[On Tuesday], we undertook an extensive search in Pheasants Nest, focusing on the southbound Hume Highway service station where Mr Gasovski’s grey Hyundai iLoad van was found."

He said the northbound service station and nearby bushland were also searched, and police left posters in the service stations to help jog the memories of motorists who regularly passed through the area.

He added the public had an important role to play in helping them do so.

“Please remember, Mr Gasovski had a loving wife and four children," he said.

"They are naturally devastated by what has happened, and deserve some form of closure."

“If you have information that may assist our investigation, do the right thing and get in touch.”